<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <!-- 开发版本 -->
    <link rel="stylesheet" href="static/plugins/bootstrap-3.4.1/css/bootstrap.css">

    <!-- 生产版本 -->
    <!-- <link rel="stylesheet" href="BootStrap_study/plugins/bootstrap-3.4.1/css/bootstrap.min.css"> -->

</head>
<body>



<!-- Extra small button group -->
<div class="btn-group">
    <button class="btn btn-default btn-xs dropdown-toggle" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
        Extra small button <span class="caret"></span>
    </button>
    <ul class="dropdown-menu">
        ...
    </ul>
</div>



<input type="submit" value="提交" />
<input type="submit" value="提交" class="btn btn-primary">
<input type="submit" value="提交" class="btn btn-success">
<input type="submit" value="提交" class="btn btn-danger">
<input type="submit" value="提交" class="btn btn-primary btn-xs">


</body>
</html>